Understanding the Influence of Lewis Acids on CO2 Hydrogenation: The Critical Effect Is on Formate Rotation

Abstract

Lewis acids (LAs) have been shown to accelerate hydrogenation of C0₂, but the underlying mechanistic details remain to be elucidated. We have employed computational methods to investigate how LAs affect CO₂ hydrogenation with a range of known metal-hydrides (L_nIr–H, L_nRu–H, L_nMn–H, L_nCo–H). Our results show that LAs can alter the nature of the hydride–CO₂ bond formation step, but do not lower its barrier. Instead, the accelerating effect of LAs is on the subsequent step, the rearrangement of the metal-formate σ-intermediate. These insights are essential for understanding the effect of LA additives on metal-mediated hydrogenations of CO₂.